Trunked radio systems allow communication units that are functionally related to one another (e.g., separate law enforcement groups such as traffic enforcement, detectives, patrol officers, etc.) to be logically grouped together into associated talkgroups. Talkgroups can also be grouped together to form multigroups (e.g., local and county-wide police departments). As the size and complexity of trunked radio systems have grown, with them have grown the desire by radio users and by the operator/dispatcher for increased multi-communication group capabilities.
U.S. Pat. No. 5,423,061 to Fumarolo et al., commonly assigned to the same assignee as the instant case, discloses various improved ways for enhancing multi-communication group capabilities including allowing a plurality of talkgroups to be selected simultaneously and allowing a dispatch console operator to temporarily merge or regroup talkgroups, with the resulting merged entity defined as a supergroup, prior to a message transmission (as in an emergency situation where talkgroups are merged/regrouped on the fly and as a function of the type of emergency occurrence).
The problem with trunked radio systems is that they cannot be effectively monitored and recorded very easily due to their complexity. During normal operation, each individual radio involved in a talkgroup call receives and detrunks the transmissions in its talkgroup. In this regard, each individual radio listens to the frequency assignment instructions from a controller of the trunked radio system and "follows" transmissions (associated with that talkgroup call) as they move from one frequency to another.
Call loggers, or call log recorders as they are also known, are well known for monitoring and recording such two-way radio voice transmissions in a trunked radio system. Typically, trunked call loggers monitor and record the individual talkgroups on a multi-track or multi-channel recorder, capturing on a tape media for example, the individual transmissions of many different talkgroup calls associated with a particular radio channel.
In early call loggers, the playback of a talkgroup call/conversation involved considerable effort requiring non-automatic assembly of scattered transmissions stored on separate tracks of a tape or the like media, where each track holds the transmissions occurring over a designated channel.
More recently, more novels approaches have been implemented or proposed for improving the playback function of multi-track or multi-channel recorders. One such method is described in an article entitled, "Overcome the Challenges of Monitoring Trunked Radio", by Carl Swift, in Communications Magazine, published January of 1996, pp. 12-14. Swift describes a call logging implementation whereby the audio associated with a given group call is detrunked prior to recording and stored on a designated recorder track, while simultaneously another call from a different group call is also being recorded (in parallel fashion) on a different designated track. Detrunking devices or trunked radios follow the conversations in a pre-set talkgroup, and the subsequent audio is recorded on a designated track of the multi-track recorder.
Multiple trunked radios may be used to do detrunking (prior to recording), but a more common and efficient way to achieve detrunking is with modified dispatch (console) equipment. When using the modified dispatch equipment approach, audio for each talkgroup is placed on separate recorder tracks subsequent to recording. When using the multiple trunked radios approach, the over-the-air audio is captured while another device simultaneously captures the system call data. The call data is recorded simultaneously with the audio, allowing later retrieval of the call audio based on the recorded call data. More conventional call loggers now employ a vox switch which analyzes the information to be recorded and removes certain parts of the information (e.g., periods of silence) prior to recording. This allows for somewhat more efficient use of resources.
Large systems--multi-site systems, in particular--require an economical means of logging trunked audio because such systems generally have high numbers of both repeaters and talkgroups. Presently, a dedicated, predefined track or channel is required for each talkgroup. Given the present state of technology, several recorders may be required. Also, because supergroups typically are non-defined and exist or are setup typically by a console operator for only a short indefinite period, the requirement that tracks are designated to all predefined talkgroups makes intelligent retrieval of supergroup calls, difficult. In Motorola's logger for its SmartZone.TM. trunking system, for example, supergroup audio is recorded on all tracks corresponding to the talkgroups within the supergroup. Hence, every track associated with a regrouped talkgroup contains the same call audio. This is an inefficient, redundant and expensive way to accomplish regroup call recording.
Typically, when a radio unit affiliates with a particular talkgroup, that radio unit, by extension, automatically gets any predefined multi-group assignments. Multigroups are sometimes also called announcement groups, since they allow a group of talkgroups to be further grouped for the purposes of making generalized transmissions. For example, a first talkgroup A may consist of all police detectives within a given region, a second talkgroup B may consist of all beat police officers in the same region, and a third talkgroup C may consist of all traffic enforcement officers again in the same region. Assuming all three talkgroups commonly belong to a singularly defined multi-group M, when any one of the talkgroup members switches to multi-group M and transmits, all the members of talkgroups A, B and C will be dynamically forced onto appropriate transmit/receive channel(s) during the transmission so as to be able to participate in the multi-group call. When the originator of the multi-group call ends the multigroup transmission, all the members of the multi-group automatically return to a state in which they monitor the talkgroup they were on just before the multi-group switch.
Quite often it is important to playback all transmissions heard on a particular radio, including not only transmissions received while re-affiliating to a new talkgroup (e.g., radio switched from talkgroup A to talkgroup B) but also multi-group M messages or announcements received while affiliated in, for example, talkgroup C or supergroup messages. Previous generation call loggers do not have the capability to playback everything heard by an individual radio unit. While current technology allows monitoring everything heard by users monitoring a particular talkgroup, conventional search algorithms don't allow selective retrieval of specific call types, nor do they support flexible logical combinations of calls, call types, and IDs.
Referring again to the Swift article, it describes a call logging scheme whereby non-detrunked call audio is digitized, compressed and stored along with call data (trunking control channel instructions). During digitizing and compression of the audio, silence is eliminated, and thereafter combined with the call data to form data packets which may then be indexed and stored on a hard disk. To recover a conversation, the user specifies a time window and a talkgroup number, name or individual radio ID. The digital recording device (logger) searches the disk to locate the desired conversations. When they are found, the recorder assembles the individual data packets of the desired conversation and replays them for review.
The Swift article is silent on how undefined talkgroup calls (i.e., multi-groups and supergroups) are handled. The conventional manner of retrieval in the logging industry for systems which detrunk on playback appears to be to specify the supergroup or multigroup ID of the desired calls explicitly rather than to treat the supergroup or multigroup ID as one of several that a talkgroup may dynamically take on over time.
The instant invention treats the ID in use at any one time as a dynamic element which can be used to derive other search parameters and looks at the logging problem as one of "What would a radio monitoring a talkgroup having this ID hear?" rather than, as logging products do today, one of "What calls were made on talkgroups having this ID?" This invention improves upon the state of the logging art by considering these extra, simultaneous-to-the-talkgroup IDs, when deciding what audio to retrieve and play back for the listener.
There is a need for improved system, of the type which detrunks on playback, which allows for more efficient retrieval of supergroup and multigroup call audio and includes enhanced search features for the logging recorder user.